1. Field of the Invention
The present invention relates to a hydraulic excavator such as primarily a hydraulic excavator of which rotating radius is small.
2. Description of the Related Art
FIG. 7 shows the prior art described in Japanese Patent Laid-Open Hei 4-181009. In the hydraulic excavator shown in FIG. 7, reference number 1 represents a boom. Mounting bracket 2 is located in the bottom end section of the boom 1. A joint pin 3 is mounted on the mounting bracket 2. One end of said joint pin 3 is blocked by a cabin 4. However, there is no interference device on the other end of the joint pin 3. Namely, there is no devices interfering with the joint pin 3 when extracting the joint pin in the direction A Accordingly, in order to pull out the joint pin 3, as FIG. 7 shows, an upper rotating body 6 is turned in the direction perpendicular to a lower traveling body 5. Next, a stationary object 7, and an extraction plug 8 mounted on the joint pin 3 are connected with a wire 9. After that, the lower traveling body 5 is moved in the direction of arrowhead C to remove the joint pin 3, thereby enabling the joint pin 3 to be pulled out from the mounting bracket 2 in the direction of arrowhead A.
FIG. 8 shows the prior art described in Japanese Utility Model Laid-Open Sho 61-2557. In the boom mounting apparatus shown in FIG. 8, on one side of the boom mounting section of a swing frame 10 a boss 11 is used. On the contrary, the other side thereof is provided with a U-shape pin bearing 12. The U-shape pin bearing 12 has four bolting female screws 13. A pin crossarm brace 14 is to be attached by four bolts 17 with spring washers 15 and flat washers 16. Accordingly, when attaching and detaching the boom, it is not necessary to pull out the joint pins in the horizontal direction, and the boom can be attached or detached without removing obstructions such as the cabin, fuel oil tank, etc.
Recently, a lot of kinds of hydraulic excavators of which rotating radius is small, designed to be suitable for work in urban areas, are produced. This type of hydraulic excavator is provided with a cab installed on one side of the boom mounting section of the upper rotating body, and with oil tanks such as hydraulic oil tank and fuel oil tank on the other side thereof.
Accordingly, it is difficult to attach and detach the joint pin for connecting the boom. Further, in the boom mounting apparatus of the prior art shown in FIG. 8, the bearing for pivotably supporting the pin installed in the rotating frame 10 is formed into a split type bearing consisting of the U-shape pin bearing 12 and the pin crossarm brace 14 to damp the pin with the bolts. In the case of the prior art shown in FIG. 8, when the hydraulic excavator is executing an excavation work, a large impact is repeatedly applied to the bolt 17, thereby shortening the period of durability of the bolt 17. In addition, problems on maintenance may arise.